Coal hydrogenation process

ABSTRACT

A PROCESS FOR HYDROGENATION OF COAL WHERE A SLURRY OF PULVERIZED COAL IN A HYDROGEN DONOR SOLVENT IS HYDROGENATED IN THE LIQUID PHASE IN THE ABSENCE OF CATALYST, VAPORS FROM THIS FIRST HYDROGENATION ARE THEN SUBJECTED TO A VAPOR PHASE HYDROGENATION IN THE PRESENCE OF A SULFIDED CATALYST AND THEREAFTER THE PRODUCTS OF THE REACTION ARE SEPARATED.

July 20 v1971 M. c. KIRK, Jan, E-rAL 3,594,303

COAL HYDROGENATION PROCESS Filed Feb. 18. 1970 5% Rw lAll NYN HU NIJS www mvcnfons: MERRITT C. K|RKJR.

H. SEITZER Auen-r WALT M United States Patent O 3,594,303 COAL HYDROGENATION PROCESS j Merritt C. Kirk, Jr., Thornton, and Walter H. Seitzer,

West Chester, Pa., assignors to Sun Oil Company,

Philadelphia, Pa.

Filed Feb. 18, 1970, Ser. No. 12,195 Int. Cl. (110g 1/08 U.S. Cl. 208-8 6 Claims ABSTRACT OF THE DISCLOSURE A process for hydrogenation of coal where a slurry of pulverized coal in a hydrogen donor solvent is hydrogenated in the liquid phase in the absence of catalyst, vapors from this rst hydrogenation are then subjected to a vapor phase hydrogenation in the presence of a sulfded catalyst and thereafter the products of the reaction are separated.

Thermal degradation processes for coal liquefaction whereby hydrogen is supplied by a liquid donor solvent are known. In such processes, the function of the catalyst is to rehydrogenate the solvent by adding molecular hydrogen to it and thus the solvent acts as a medium to carry hydrogen from the solid catalyst to the solid coal. However, the catalyst is rapidly deactivated with the result that the process is highly inefficient and not conducive to a commercial coal hydrogenation process.

An improved coal hydrogenation process is now provided whereby catalyst deactivation is prevented, and in addition, other benefits are achieved. For example, the process of this invention is carried out at relatively low temperatures and results in the minimum production of gaseous products; instead, the process of the invention yields a greater proportion of more desirable liquid hydrocarbon products. In accord With the process, hydrogenation of coal is achieved in a highly eicient procedure by subjecting a slurry of pulverized coal in a hydrogen donor solvent to a liquid phase, non-catalytic thermal coal liquefaction in the presence of hydrogen at a temperature from about 750 to about 840 F. and at a pressure of about 2500 p.s.i.g., conducting the vapors from said liquid phase hydrogenation to a hydrogenation zone containing a supported sulded catalyst wherein hydrogenation is conducted at about 700 to 800 F. and at about 2500 p.s.i.g., and separating products of the reaction process into gas, naphtha, light gas oil and heavy oil fractions.

An essential and critical feature of the invention is that the pulverized coal to be liquefied is slurried with a hydrogen donor solvent. These donor solvent materials are well known and comprise aromatic hydrocarbons which are partially hydrogenated, generally having one or more of the nuclei at least partially saturated. Several examples of such materials are Tetralin, dihydronaphthalene, dihydroalkylnaphthalenes, dihydrophenanthrene, dihydroanthracene, dihydrochrysenes, tetrahydrochrysenes, tetrahydropyrenes, tetrahydrofiuoranthenes and the like. Of particular value in the process of this invention as hydrogen donor solvents are the hydrophenanthrenes and hydroanthracenes such as dihydroanthracene. It will be understood that these materials may be obtained from any source, but are readily available from the process of the invention by separating hydrocarbon fractions formed in the process to obtain the aromatics which have been at least partially hydrogenated, or they may be obtained by partially hydrogenating specic aromatic products by conventional techniques.

Although the process of the invention is not limited to the choice of any particular coal, it is preferred to use any of the wide variety of bituminous and sub-bituminous ice coals or lignite and of these it is preferred to use Illinois No. 6 or Wyoming sub-bituminous type coal.

The catalysts used in the second phase of the process where a vapor phase hydrogenation occurs are well known and commercially available catalysts and any of the usual suled hydrogenation catalysts may be used. Preferably a cobalt oxide-molybdenum oxide catalyst (referred to as cobalt-molybdenum catalyst) supported on alumina will be used, but other very effective catalysts are nickeltungsten, nickel-molybdenum and like catalysts supported on alumina, silica, silica-aluminates, or the like. These catalysts may be prepared by the methods given in an article by Beuther et al. appearing in the American Chemical Society, Petroleum Division Papers, vol. 3, 1958, page 35. The catalysts are sulfded (that is, subjected to HZS vapors) either before or during start-up of the process. Commercially available catalysts which are particularly useful include Aero HDS-2 (a cobalt-molybdenum catalyst) and HDS-3 (a nickel-molybdenum catalyst), both sold by Cyanamid.

Another significant factor in making the process of this invention operative and providing for full benets of the invention is the use of relatively large volumes of the hydrogen donor solvent with respect to the pulverized coal. The minimum amount of solvent to be used will be about 1 part of solvent to 1 part of coal on a weight basis. On the other hand, where a large amount of solvent is used, there is no need to exceed a weight ratio of about 2:1.

Still another important consideration in the process is the large volume of hydrogen that is employed and the rate at which it is introduced into the reactor.

Three factors must be considered in determining the hydrogen rate of addition: (1) the minimum rate is that required for chemical consumption; (2) there must be enough in the thermal zone to carry the spent donor solvent and product hydrocarbon vapors into the catalytic zone; and (3) enough hydrogen must be supplied to the catalytic zone to absorb the exothermic heat of hydrogenation and maintain temperature control. In the process, the chemical consumption of molecular hydrogen will be about 20,000 s.c.f. (standard cubic feet) per ton of dry coal fed. It will take nearly 500,000 s.c.f. recycle gas per ton to absorb the heat of reaction and control the temperature, but since this would be so much gas in the thermal zone as to cause ooding and entrainment, it is best to operate at about 150,000 s.c.f. per ton to the thermal zone and 350,000 s.c.f. per ton to the catalytic zone. This hydrogen gas will be made up from both fresh and recycle hydrogen.

The time of reaction in the first stage thermal liquefaction zone will vary from about 10 minutes to about l hour and will preferably be about 20 minutes. In the catalytic zone the liquid hourly space velocity (LHSV) will vary from about 0.1 to about 10 vol./vol./hr. with 0.5 vol./vol./hr. preferred, based on total oil thruput of about l0 barrels (spent donor solvent plus product oil) per ton of dry coal fed.

In order to further describe the invention, reference is now made to the drawing.

Pulverized coal together with the hydrogen donor solvent which may be from any source (but is preferably obtained from the reaction process itself by hydrogenation of the coal and subsequently separated) is fed into slurry tank 1 where the slurry is taken through line 2 to the liquid-phase thermal coal liquefaction zone (bottom section) of reactor 3. Hydrogen is also introduced to this reactor through line 4 and comprises fresh and recycle gas as shown as line 8 and 8a. Reaction conditions in this liquid-phase zone are temperatures of about 750 to about 840 F. and pressures on the order of 2500 p.s.i.g. No

3 catalyst is present in this phase of the process. Hydrogenation proceeds and vapors of the hydrogen donor solvent and reaction products pass upwardly through reactor 3 into the vapor-phase catalytic hydrogenation zone (top section). It will be understood, of course, that although both the liquid-phase thermal liquefaction zone and vapor-phase catalytic hydrogenation zone are shown in the drawing in a single reactor, this process is equally operable by separating these two stages and using separate reactors for each stage. In the catalytic hydrogenation zone, which contains a supported catalyst as described above, reaction temperatures of about 700 to 800 F. and pressures of about 2500 p.s.i.g. are maintained. Ash containing resid which remains in the rst liquid-phase thermal coal liquefaction zone is not able to enter the vapor phase catalytic hydrogenation zone and thus has no adverse effect on the catalyst. As ash builds up in the liquid phase zone, it may be removed through line 5 for further processing if desired, as for example, for carbonization or for hydrogen manufacture. The volatile products resulting from the catalytic hydrogenation zone are taken oi through line 6 into a separator 7 and hydrogen is recycled through line 8a to the reactor. The heavier products are fed to line 9 into a fractionator 10 to produce fractions of naphtha, light gas oil and heavy gas oil. The naphtha may, of course, be separated into a lighter gas fraction by passing part of the naphtha through line 11 into separator 12 to remove the more volatile gas. One of the fractions from fractionator will be the hydrogen donor solvent which is taken through line 13 back to the original slurry tank 1 for mixing with the pulverized coal.

As will be observed from the drawing and the description, the process is extremely simple and produces useful products from coal in a very highly eil'cient and economical manner.

The invention claimed is:

1. A process for hydrogenation of coal which cornprises subjecting a slurry of pulverized coal in a hydrogen donor solvent to a liquid-phase, non-catalytic thermal coal liquefaction in the presence of hydrogen at a temperature of from about 750 to 840 F. and at a pressure of about 2500 p.s.i.g., conducting the vapors from said liquid phase to a hydrogenation zone containing a supported sulfided hydrogenation catalyst wherein hydrogenation is conducted at about 700 to 800 F. and at about 2500 p.s.i.g., and separating products of the reaction to gas, naphtha, light gas oil, and heavy gas oil fractions.

2. A process for hydrogenation of coal which comprises subjecting a slurry of pulverized coal in a hydrogen donor solvent to a liquid-phase, non-catalytic thermal coal liquefaction in the presence of hydrogen at a temperature of from about 750 to 840 F. and at a pressure of about 2500 p.s.i.g., said slurry having a weight ratio of donor solvent to coal 0f between about 1:1 and 2:1, conducting the vapors from said liquid phase to a hydrogenation zone containing a supported sulded catalyst of the oxides of cobalt and molybdenum, or nickel and molybdenum, wherein hydrogenation is conducted at about 700 to 800 F. and at about 2500 p.s.i.g., and separating products of the reaction to gas, naphtha, light gas oil and heavy gas oil fractions.

3. The process of claim 2 wherein the catalyst comprises a sulded cobalt-molybdenum catalyst on alumina.

4. The process of claim 2 wherein the catalyst comprises a nickel-tungsten catalyst on alumina.

5. The process of claim 3 wherein the donor solvent is dihydroanthracene.

6. The process of claim 3 wherein the donor solvent is a product of the process and is recycled to form a slurry with powdered coal.

References Cited UNITED STATES PATENTS 3,488,279 1/1970 Schulman 308-10 3,143,089 8/1964 Gorin 208-10 2,885,337 5/1959 Keith et al 208-8 DELBERT E. GANT Z, Primary Examiner V. OKEEFE, Assistant Examiner 

